The present invention relates to a variable region of the monoclonal antibody against S-surface antigen of hepatitis B virus and a gene encoding the same, a recombinant vector containing the said gene, and a transformant obtained from the said recombinant vector.
Hepatitis B virus (hereinafter, referred to as xe2x80x9cHBVxe2x80x9d), known as the Dane particle, has a spherical feature of 42 nm diameter. The outer envelope contains a large amount of hepatitis B surface antigens and surrounds the inner nucleocapsid composed of 180 hepatitis B core proteins. The nucleocapsid contains HBV genome, polymerase, etc (Summers et al., Proc. Nat. Acad. Sci, 72, 4579, 1975; Pierre Tiollais et al., Science, 213, 406-411, 1981).
Within the HBV genome, the coding region of HBV surface antigens contains three open reading frame start sites which share a common termination codon producing same S domain. Thus, the HBV surface antigens may be classified into three types, i.e., (1) Small HBV Surface Antigen (hereinafter, referred to as xe2x80x9cS-surface antigenxe2x80x9d), containing only the S domain, (2) Middle HBV Surface Antigen (hereinafter, referred to as xe2x80x9cM-surface antigenxe2x80x9d), containing the S domain and an additional 55 amino acid domain known as Pre-S2, and (3) Large HBV Surface Antigen (hereinafter, referred to as xe2x80x9cL-surface antigenxe2x80x9d), containing the Pre-S1 domain as well as the Pre-S2 and S domain. Among the expressed surface antigens, S-surface antigen is about 80% or more.
Subtypes of S-surface antigen were classified according to their properties of antibody recognition. Antigenic domains expressed in all surface antigen were classified as determinant a. The four other subtypes are d or y and w or r. Determinant d has a lysine at residue 122 while y has arginine. Similarly, determinant w has a lysine at residue 160 while r has arginine (Kennedy R. C. et al., J. Immunol. 130, 385, 1983). Thus, serological types can be classified into four subtypes, such as adr, adw, ayr and ayw (Peterson et al., J. Biol. Chem. 257, 10414, 1982; Lars O. Marnius et al., Intervirology, 38, 24-34, 1995).
The S-surface antigen specifically binds to hepatocyte (Leenders et al., Hepatology, 12, 141, 1990; Irina Ionescu-Matiu et al., J. Med. Virology, 6, 175-178, 1980; Swan N. T. et al., Gastroenterology 80, 260-264, 1981; Swan N. T. et al., Gastroenterology, 85, 466-468, 1983; Marie, L. M. et al., Proc. Nat. Acad. Sci. 81, 7708-7712, 1984). And, it has been identified that human hepatic plasma membrane contains target proteins such as apolipoprotein H and endonexin II which specifically bind to S-surface antigen (Mehdi H. et al., J. Virol., 68, 2415, 1994; Hertogs K. et al., Virology, 197, 265, 1993).
Meanwhile, in developing an useful therapeutic monoclonal antibody, a humanized antibody is preferable because monoclonal antibodies obtained from mice could cause an immune response when applying to human.
The Korean patent publication No. 1999-8650 has recently disclosed a variable region of the monoclonal antibody against a Pre-S1 epitope which solely exists in a L-surface antigen among the three HBV surface antigens (S-, M-, and L-surface antigens), a gene encoding the same, and a humanized antibody using the same. Because the L-surface antigen is only 1xcx9c2% of the expressed surface antigens, however, the L-surface antigen is inappropriate as a target for anti-HBV antibody development for diagnostic as well as therapeutic purposes.
Accordingly, a primary object of the present invention is to provide a gene encoding the variable region of a monoclonal antibody, specifically recognizing the S-surface antigen, especially determinant a, which commonly exists in all of the HBV surface antigens.
It is another object of the present invention to provide a recombinant vector comprising the above gene.
It is a further object of the present invention to provide a transformant obtained using the above recombinant vector.
It is still another object of the present invention to provide a variable region of the above monoclonal antibody.
In accordance with one aspect of the present invention, provided is a gene encoding the monoclonal antibody variable region which specifically recognizes the HBV S-surface antigen.
The present inventors immunize mice with the determinant adr type of S-surface antigen (International Enzymes Inc., USA) which is most frequently found in Korean HBV patients. The spleen cells obtained from the immunized mice were fused with myeloma cells (SP2Oxe2x80x94Ag14, ATCC CRL-1581) to generate a large number of hybridoma cells which, following subsequent cloning and selection procedures, eventually give rise to numerous monoclonal antibodies. The present inventors selected monoclonal antibodies specifically binding to the determinant a among the numerous monoclonal antibodies; and as a result, obtained a hybridoma cell line (A9-11-5) producing a distinct monoclonal antibody which specifically binds to the determinant a with high binding affinity.
The present inventors isolated total RNAs from the said hybridoma cell line to synthesize the cDNAs of light and heavy chains, and finally, obtained about 440 bp of light chain cDNA gene comprising SEQ ID NO. 5 and about 460 bp of heavy chain cDNA gene comprising SEQ ID NO. 6, respectively.
From the said monoclonal antibody light and heavy chains, the CDR (complementarity determining region) residues were detected. As a result, it is identified that the CDR residues of the light chain exist at the positions of 23-36, 52-58, and 91-98 representing the peptides of SEQ ID Nos. 9, 10, and 11, respectively. Further, it is found that the CDR residues of the heavy chain exist at the positions of 31-35, 50-65, and 98-103 representing the peptides of SEQ ID Nos. 12, 13, and 14, respectively.
Accordingly, the present invention includes, within its scope, a cDNA encoding a light chain variable region of a monoclonal antibody against a HBV S-surface antigen, the said light chain variable region comprising the peptides of SEQ ID Nos. 9, 10, and 11. Further, the present invention includes a cDNA wherein the light chain variable region has the amino acid sequence of SEQ ID NO. 7, and preferably, a cDNA comprising the nucleotide sequence of SEQ ID NO. 5.
And also, the present invention includes, within its scope, a cDNA encoding a heavy chain variable region of a monoclonal antibody against the HBV S-surface antigen, the said heavy chain variable region comprising the peptides of SEQ ID Nos. 12, 13, and 14. Further, the present invention includes a cDNA wherein the heavy chain variable region has the amino acid sequence of SEQ ID NO. 8, and preferably, a cDNA comprising the nucleotide sequence of SEQ ID NO. 6.
The above cDNA genes encoding the light or heavy chain variable region of a monoclonal antibody may be inserted into plasmid vector such as pCRII (Invitrogen Co. USA) to give recombinant vectors. Accordingly, the present invention includes, within its scope, a recombinant vector pCRA9Lv comprising the above cDNA encoding a light chain variable region and a recombinant vector pCRA9Hv comprising the above cDNA encoding a heavy chain variable region.
Further, microorganisms, such as E. coli, may be transformed with the above recombinant vectors, pCRA9Lv and/or pCRA9Hv, to obtain transformants. Accordingly, the present invention includes a transformant E. coli DH5/YRC-pCRA9Lv (KCTC 1011BP) and a transformant E. coli DH5/YRC-pCRA9Hv (KCTC 1010BP) which are transformed with a recombinant vector pCRA9Lv and pCRA9Hv, respectively.
Recombinant vectors may be recovered from the above transformants using known methods (J. Sambrook et al., Molecular cloning, Vol. 1, 1.25-1.28). For example, the cell membrane of a transformant may be weakened with solution 1 (50 mM glucose, 25 mM Tris.HCl, and 10 mM EDTA). With solution 2 (0.2N NaOH and 1% SDS) the cell membrane may be destroyed and proteins and chromosomes may be denatured. The ingredients other than recombinant vectors may be aggregated with solution 3 (5M potassium acetate and acetic acid) and then centrifuged. The obtained recombinant vector layer may be precipitated with ethanol to recover recombinant vectors.
The present invention includes, within its scope, a monoclonal antibody variable region, which consists of a light chain comprising the peptides of SEQ ID Nos. 9, 10, and 11 and a heavy chain comprising the peptides of SEQ ID Nos. 12, 13, and 14. Further, preferable is a monoclonal antibody variable region, wherein the light chain variable region has the amino acid sequence of SEQ ID NO. 7 and the heavy chain variable region has the amino acid sequence of SEQ ID NO. 8.
From the above cDNA genes encoding a monoclonal antibody variable region according to the present invention, a humanized monoclonal antibody against HBV may be obtained by fusing the CDR region where S-surface antigen binds directly (i.e., in case of the light chain, the gene encoding the peptides of SEQ ID Nos. 9, 10, and 11; and in case of the heavy chain, the gene encoding the peptides of SEQ ID Nos. 12, 13, and 14) to a human antibody gene, or by substituting a human antibody variable region with a gene encoding the monoclonal antibody variable region according to the present invention.
As mentioned above, the gene encoding the monoclonal antibody variable region according to the present invention is specifically effective in the recognition of HBV S-surface antigen, especially determinant a, which has the highest expression ratio in the HBV surface antigens. Therefore, the gene according to the present invention may be used to manufacture monoclonal antibodies which may be widely applied to various types of HBV surface antigens, such as adr, adw, ayr and ayw, to neutralize and/or remove HBV.
The present invention will now be further illustrated in detail by, but is by no means limited to, the following Examples.